1. Field of the Invention
The present invention concerns a method and an apparatus for improved re-try error recovery for tape storage drives. The method and apparatus are based on an n-dimensional array of symbols (typically bytes) that are ECC coded with a symbol correcting code (typically an RS code) in each dimension (product code scheme).
2. Description of the Prior Art
When a storage system, such as a tape storage system, reads data from a storage medium, such as tape, erroneous data will be received occasionally because of defects in the medium, tape debris, etc. When erroneous data are detected by an error detection system, an attempt is made to correct the data, or to test the data to determine if the data can be corrected. If the correction process is not successful, the tape must be rewound, and data have to be read again. This is referred to as a re-read. After the re-read is performed, the error detection and error correction process is repeated. The re-read process and the ECC process are performed a predetermined number of times. If the error cannot be corrected after the predetermined number of tries, the data cannot be recovered and the error is referred to as a “fatal” error. The re-read and ECC processes have conventionally been performed as two separate processes for tape storage systems.
U.S. Pat. No. 6,920,005, however, discloses combining the re-read process for a storage apparatus with the error correction process. In the procedure disclosed in the U.S. Pat. No. 6,920,005, the performance of a current error recovery operation is compared with the performance of a previous error recovery operation. This is accomplished by applying parameters to the recovery process, and comparing the performance, such as channel statistics, of the recovery operation with those of a previous recovery operation, and then adding parameters.